Electric and hybrid electric vehicles often use sources of high voltage such as battery packs or fuel cells that deliver direct current (DC) to drive vehicle motors, electric traction systems (ETS), and other vehicle systems. An ETS is typically under the control of a variable motor drive (VMD) module that generally includes at least one power inverter system designed to convert the DC source input signal to an alternating current (AC) output signal compatible with electric motors and other various electrical components. Such power inverter systems generally include both integrated gate bipolar transistor (IGBT) and capacitor modules interconnected by bipolar busbar and/or cabling assemblies that distribute current throughout the inverter.
The IGBT module generally includes a plurality of individual power modules for converting the DC input signal to an AC output signal. Because accompanying electronic components such as AC and DC cables, busbar assemblies, and other discreet and integrated components such as power diodes and individual IGBTs often have inherent capacitance and/or inductance, such cycling can generate stray AC currents (or “common mode” currents). Common mode currents can produce generally undesirable electromagnetic interference (EMI) radiation that can adversely affect the performance of other nearby radio frequency-based electronic systems such as radio receivers, cellular phones, and the like. Because EMI emissions generally increase with the distance that common mode currents travel from ground to reach their positive or negative busbar source, power inverters on many vehicles include filtering capacitors within a grounded inverter chassis connected between busbars and/or cabling and the chassis that provide such currents with a shortened, low impedance pathway from ground to source.
However, filtering capacitors configured in this manner present several drawbacks. Capacitor filters are located away from the power modules and IGBT devices where many common mode currents originate. As a result, the “loop area” or area circumnavigated by these currents on the ground path may be sufficient to create considerable levels of EMI radiation. This condition is potentially enhanced in vehicles wherein the power inverter chassis and DC source have appreciable separation. Further, achieving a reliable connection between capacitor electrodes and busbar/chassis surfaces can be especially challenging, and often adds significantly to fabrication/assembly cost and complexity.
Accordingly, it is desirable to provide a power module assembly with reduced EMI radiation. Further, it is also desirable if such an assembly is simpler to fabricate. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.